John, there are probably others on here with a 90 size JAE rigger who can add information. I don't own a 90 rigger. But all the other JAE riggers if set up via the instructions have worked very well for me. Strut down against ski. Usually 0 degrees on the angle. Possibly 1 to 2 degrees at most. I don't know what issues that you are having. But odds are it is a prop issue if boat is setup per the instruction. If it is a turning issue. Although some say that CG is not an issue with the JAE riggers. I disagree with that. Check CG location on the turn fin.
I have many variations of JAE 12, 21, 45 riggers. All are setup per the instructions and handle very well.